Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $182.60   8.194%   $197.5622   $197.56   $197.55   $197.60  
  Purchase #2 $149.93   7.664%   $161.4206   $161.42   $161.40   $161.40  
  Purchase #3 $236.70   10.309%   $261.1014   $261.10   $261.10   $261.10  
  Purchase #4 $180.82   13.566%   $205.35   $205.35   $205.35   $205.40  
  Purchase #5 $25.43   4.460%   $26.5642   $26.56   $26.55   $26.60  
  Purchase #6 $250.88   6.239%   $266.5324   $266.53   $266.55   $266.50  
  Purchase #7 $219.36   9.319%   $239.8022   $239.80   $239.80   $239.80  
  7 purchase totals = $1,245.72       $1,358.3330   $1,358.32   $1,358.30   $1,358.40